This proposal describes a carefully supervised program that will provide the applicant with research skills and training in molecular virology, viral pathogenesis, and experimental design. Herpes simplex causes significant human illness, particularly in those who are immunocompromised, for whom a reactivated infection can be fatal. Following acute primary infection, the virus remains latent in nerve cells for the life of the host. Nigel Fraser's group is recognized as one of the leading laboratories studying herpes simplex latency. Under Dr. Fraser's sponsorship, the proposed research will investigate how altered expression of viral transactivating proteins alpha trans-inducing factor (alpha-TIF) and immediate-early gene (ICPO) affects the regulation of HSV-1 transcription during latency. In Phase I, a firm background in molecular biology and virology will be provided by a structured didactic program and an intensive laboratory experience. Recombinant HSV-1 viruses will be engineered to express viral regulatory proteins ICPO and alpha-TIF (VP16), under the control of the LAT (latency-associated transcript) promoter. This promoter is active in latently infected neurons of the peripheral and central nervous system. The viruses will be plaque-purified, and their altered ability to express these regulatory proteins will be characterized. During Phase II, these recombinant viruses will be tested in an animal model of latency in order to determine the effect of viral expression of VP16 and ICPO on the establishment, maintenance and reactivation of HSV latency in the nervous system. The skills and knowledge acquired during the completion of these studies will be broad-based and comprehensive providing the applicant with a substantial foundation for future investigations into other areas of viral pathogenesis and neurovirology.